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what shapes the three dimensional organization of tissues?
cell cell and cell-matrix interactions; every cell has unique architecture particular to cell type
what are the 5 major groups of proteins of ECM?
- collagens (most abundant)
- elastin (contain glycoproteins)
- proteoglycans (specific sugar groups)
- adhesive glycoproteins
why does distinct cell types secret a variety of ECM proteins and in differing proportions?
EMC in distinct tissues is specialized for particular functional needs (tendons, blood vessel walls)
where are networks of collagen most commonly found?
basal laminae, that underlie epithelia, required for polarization
how are collagen fibers organized?
single collagen polypeptide chain, triple stranded collagen molecule, collagen fibril and collagen fibers
describe the molecular structure of collagen molecules
- rod shaped, triple helices, contain series of triplet sequence (Gly-X-Y)
- X is commonly proline, Y hydroxyproline
- consists of three left handed helices, form a larger helix, packing glycines at the center
- 25% vertebrate body weight
when can cells order the collagen network?
after it is secreted
what is a main component of connective tissue?
what is the most abundant protein in mammals?
collagen (25-35% of whole body protein content)
what is the shape of collagen and where is it commonly found?
- in the form of elongated fibrils, it is mostly found in fibrous tissues such as tendon, liagment, and skin, cornea, cartilage, bone, blood vessels, the gut and intervertebral disc
- elastic and bendable with mechanical properties
what produces fibrillar collagen?
what kind of collagen is found in tendons, bones and connective tissue?
provide tensile strength
what are the different isoforms of collagen, how are they different?
fibrillar, sheet forming, anchoring/linking; vary in size and shape according to their function
what is the role of protein disulfide isomerase in collagen biosynthesis?
- folding of collagen via the formation of globular structure on the COOH ends, which ensures
- 1)correct selection of alpha-chains
- 2)aligns 3 polypeptides with their C terminal Gly-X-Y repeats in register
- 3)prevents pre-mature assembly of fibrils during transit through Golgi network
what is the funciton of prolylpeptide isomerase?
catalyzes the interconversion of trans-proline peptide bonds
what is the role of procollagen proteases?
work to cleave pro-peptides, allowing collagen to self assemble into fibrils
what type is the sheet-forming collagen?
- polymerize into sheets that surround organs and tissues
- type 4 collagen is mostly commonly found in basal lamina
what kind of collagen organization does cornea and bone have?
alternating, plywood-type organization, going in different directions provides strength and elasticity
what kind of collagen organization does tendons have?
long parallel bundles along the axis of tension; strong and resists deformation
what kind of fibrils are found in the cartilage?
smaller, randomly oriented fibrils.
where is the network of collagen found?
in basal lamina, underlying epithelial cells.
where is the wickerwork organization found in cells?
how are bones formed?
collagen is secreted by osteoblasts and mineralization occurs by calcium phosphate deposition
how are concentric rings observed in bone?
generate by perpendicular deposition of collagen fibers
what gives the elastic characteristic to cartilage?
fibers are embedded in a hydrate network of proteoglycans (sugar) and glycosaminoglycans
what is the role of linking collagen?
link fibrillar and sheet forming collagens to other structures most anchoring fibrils are type 7 collagen
what are blisters caused by?
mutations in type 7 collagen that causes the epithelium to pull away from underlying connective tissue
what is a key component of elastic fibers?
what are elastic fibers?
- rubber lack found in connective tissue of the skin, walls of arteries and the lung
- recoil passively after tissues have been stretched
- network of fibrillin microfibrils, embedded in a core of cross linked elastin proteins
- produced by fibroblasts
what are tropoelastins?
elastin subunits, crosslinking of elastin molecules yields a ring structure that covalently corss links tropoelastins to each other
what are GAGs and proteoglycans?
long polysaccharides made up of repeating disaccharide units
what are the major components of cartilage, loose connective tissue and basement membranes?